PROBLEM TO BE SOLVED: To attain an effective restriction of vibration under a large inertia mass by integrating an inertia body with a rotating shaft member to increase a rotation moment against a specified vibration added to an object to be controlled against vibration.SOLUTION: An axial relative motion between a casing 2 and a sleeve 3 is converted into a rotating motion of a rotary shaft member 6 made of soft magnetic material by a ball screw 4 and a ball nut 5. A tight-sealed area 11 is formed between it and an outer periphery of the rotary shaft member 6, and a mass body 7 made of soft magnetic material is coaxially supported in the casing 2 with the rotary shaft member 6. Electromagnets 8 forming a magnetic field M crossing a tight-sealed area 11 with the rotary shaft member 6 and the mass body 7 being applied as a part of the magnetic circuit are fixed to the inner wall of the casing 2. Magnetic fields attained by the electromagnets 8 are applied in a first tight-sealed area 11 to cause viscosity hardness of magnetic viscous fluid to be increased, the mass body 7 is rotated in integral with the rotary shaft member 6, its rotation moment is increased and requisite inertia mass for vibration restriction is attained.SELECTED DRAWING: Figure 1
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